1. Field of the Invention
The present invention relates to a flexible coupling sleeve for a flexible shaft coupling of the sleeve type, and to a flexible shaft coupling device incorporating such sleeve.
2. Description of the Related Art
Flexible coupling sleeves for use as part of a flexible shaft coupling of the sleeve-type generally comprise a central annular- or generally cylindrical portion and a coupling receiving portion at either end of the cylindrical portion. Each of the coupling receiving portions includes a plurality of axially extending ribs or teeth along at least a portion of the inner periphery of the sleeve for meshing with grooves in oppositely disposed hubs or end pieces to form a flexible coupling. Such couplings are used to connect two rotating shafts that are coupled to the end pieces. Sleeve-type flexible shaft couplings are useful for accommodating misalignment of two shafts to be coupled together, and for providing a low noise driving connection between the shafts by virtue of their flexible cylindrical portion and the resiliency of their teeth. A coupled assembly such as a transmission comprises a spline-like driving shaft, a similar driven shaft, and a coupling operatively connecting the shafts generally along the axes thereof and in driving relation so as to transmit power therebetween. Various illustrations of sleeve-type flexible couplings and coupling sleeves for utilization in same are set forth for example in Great Britain Patent No. 879,493, in U.S. Pat. No. 2,918,809 to Miller, and in U.S. Pat. No. 6,283,868 to Clarke et al.
In sleeve-type flexible shaft couplings wherein rotation of a driver shaft in relation to a driven shaft is caused by the transmission of torque across the length of the sleeve-shaped body, which results in twisting of the coupling's central cylindrical portion, it is necessary to counter the radial force to which the coupling sleeve is exposed in use to prevent it from expanding and becoming inoperative, particularly in high- and/or variable speed applications in which early coupling failure is common. Methods that have been employed for this purpose include reinforcing the central cylindrical portion of such coupling sleeves formed of a vulcanized synthetic rubber with a highly resilient tensile cord; or forming the teeth of the sleeve so that they mechanically interlock with the corresponding grooves in the hubs or end-pieces and are thus prevented from expanding away from the grooves. It is moreover necessary to form the coupling device so that it possesses sufficient circumferential shear stress resistance for its intended application to prevent the weakest point of the coupling, i.e., it's teeth, from failing prematurely. Methods that have been employed for this purpose include covering the vulcanized synthetic rubber tooth portions of the coupling sleeve to include an outer, end-piece engaging wear-resistant textile jacket to improve the overall resilience of the sleeve's teeth.
Power transmission belts formed of a polyurethane/urea composition exhibiting improved thermal stability are known from International Patent Application Publication No. WO96/02584 to Wu et al. The teachings of WO96/02584 with respect to those applications to which the disclosed polyurethane/urea compositions find use are limited to power transmission belts, e.g., timing belts, multi-v-ribbed belts and V-belts, which are composite articles comprising both a textile reinforcement member, e.g., a tensile cord, and the polyurethane/urea flexible portion. Moreover, such belt applications call for a flexible member exhibiting a certain set of performance properties, e.g., high flex fatigue resistance and high power transmitting capability under high strain conditions. The use to which a flexible sleeve-type coupling is put conversely calls for a generally different set of performance properties, e.g., torque transmission capability under high and/or variable stress conditions, characterized by high and/or variable amplitudes and frequencies.
Moreover, innovations in automotive technology that have come about in recent years, including for example in accessory drive applications, in part as a consequence of the prominence of increasingly small engine compartments, provides increasing opportunity for the utilization of couplings in direct drive configurations. But such applications are characterized by extremely high speeds, e.g., 18,000-20,000 rpms or even higher, frequent speed changes, high accelerations and broad operating temperature requirements, e.g., −40 to 140° C. At these extremes of temperature, acceleration and speed, a highly durable, reliable and temperature-stable flexible coupling is needed.
Such a durable, reliable and, optionally, temperature-stable coupling sleeve and flexible sleeve-type coupling incorporating such sleeve that would moreover be economical to produce would be highly desirable.